** Description changed:
+ == SRU Justification, EOAN ==
+
+ ZFS can deadlock, this can be sometimes triggered with a zfs rollback -
+ "the zfs_resume_fs() code path may cause zfs to spawn new threads as it
+ reinstantiates the suspended fs's zil. When a new thread is spawned, the
+ kernel may attempt to free memory for that thread by freeing some
+ unreferenced inodes. If it happens to select inodes that are a a part of
+ the suspended fs a deadlock will occur because freeing inodes requires
+ holding the fs's z_teardown_inactive_lock which is still held from the
+ suspend."
+
+ == The Fix ==
+
+ Backport of ZFS upstream commit e7a2fa70c3b0d8c8cee2b484038bb5623c7c1ea9
+ ("Fix deadlock in 'zfs rollback'")
+
+ The backport is relatively simple context wiggle.
+
+ == Test Case ==
+
+ This is hard to trigger so testing is non-trivial. To check for
+ regressions we run the entire Ubuntu ZFS regression test suite. Without
+ the fix rollbacks can very occasionally trip this issue. With the test,
+ it's not possible.
+
+ == Regression Potential ==
+
+ The fix adds in an extra z_suspended flag to track suspended state and
+ adds an extra reference to stop the kernel from free'ing inodes on a
+ suspected file system. The changes are small and are well-used in
+ upstream ZFS so I believe if a regression was to have occurred it would
+ have been found by the regression testing.
+
+ --------------------- Original Bug Report Below -------------------
+
Hopefully this is the correct bug tracker to report this on.
Recently, I ran into a bug in ZFS as shipped in Ubuntu 19.10 that caused
the kernel to deadlock and the system to eventually hang.
I was advised by a ZFS on Linux project maintainer that this was a bug
that was fixed in 0.8.2.
The relevant pull request is here:
https://github.com/zfsonlinux/zfs/pull/9203
It would probably be a good idea to backport that pull request into
19.10's build of ZFS.
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https://bugs.launchpad.net/bugs/1847832
Title:
Backport ZoL pull request 9203 into the official packages.
Status in zfs-linux package in Ubuntu:
In Progress
Bug description:
== SRU Justification, EOAN ==
ZFS can deadlock, this can be sometimes triggered with a zfs rollback
- "the zfs_resume_fs() code path may cause zfs to spawn new threads as
it reinstantiates the suspended fs's zil. When a new thread is
spawned, the kernel may attempt to free memory for that thread by
freeing some unreferenced inodes. If it happens to select inodes that
are a a part of the suspended fs a deadlock will occur because freeing
inodes requires holding the fs's z_teardown_inactive_lock which is
still held from the suspend."
== The Fix ==
Backport of ZFS upstream commit
e7a2fa70c3b0d8c8cee2b484038bb5623c7c1ea9 ("Fix deadlock in 'zfs
rollback'")
The backport is relatively simple context wiggle.
== Test Case ==
This is hard to trigger so testing is non-trivial. To check for
regressions we run the entire Ubuntu ZFS regression test suite.
Without the fix rollbacks can very occasionally trip this issue. With
the test, it's not possible.
== Regression Potential ==
The fix adds in an extra z_suspended flag to track suspended state and
adds an extra reference to stop the kernel from free'ing inodes on a
suspected file system. The changes are small and are well-used in
upstream ZFS so I believe if a regression was to have occurred it
would have been found by the regression testing.
--------------------- Original Bug Report Below -------------------
Hopefully this is the correct bug tracker to report this on.
Recently, I ran into a bug in ZFS as shipped in Ubuntu 19.10 that
caused the kernel to deadlock and the system to eventually hang.
I was advised by a ZFS on Linux project maintainer that this was a bug
that was fixed in 0.8.2.
The relevant pull request is here:
https://github.com/zfsonlinux/zfs/pull/9203
It would probably be a good idea to backport that pull request into
19.10's build of ZFS.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/1847832/+subscriptions
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